Inboard-outboard boat propelling apparatus

ABSTRACT

Boat propelling apparatus securable to the transom of a boat and comprising an inboard prime mover and an outboard propeller unit having its propeller shaft driven from the drive shaft of the prime mover by a belt which extends over the top of the transom. A rigid supporting structure of substantially inverted U-shape provides a common mounting means for the prime mover and the propeller unit. The legs of the supporting structure straddle the transom of a boat having the apparatus mounted thereon, and the prime mover is carried by the inboard leg while the propeller unit is carried by the bight bridging the upper ends of the legs.

United States Patent [191 Carpenter 1 1 llNBOARlD-OUTBOARD BOAT PROPELMNG APPARATUS [76] Inventor: James L. Carpenter, 10649 W.

Donges Bay Rd. 104N, Mequon,

Wis. 53092 [22] Filed: July 21, 1972 121] Appl. No.: 274,090

[52] US. Cl. 115/35 [51] Int. Cl B63h 21/26 [58] Field Of Search 115/17, 18, 34 R, 34 B,

115/35, 41 R, 41 HT; 248/4 [56] References Cited UNITED STATES PATENTS 1.131.287 3/1915 Stockemann 115/35 2,209,302 7/1940 Johnson et a1 r 115/41 R 2.755.766 7/1956 Wanzer r 115/35 2,822,999 2/1958 Tromanhauser..... 248/4 2,930,342 3/1960 Wanzer.... 115/35 2,955,562 10/1960 Modes 115/35 1 June 1,1974

3,072,090 H1963 Yurbrough 115/35 Primary ExaminerTrygve M. Blix Assistant Examiner-Charles E. Frankfort Attorney, Agent, or Firm1ra Milton Jones [57] ABSTRA'CT Boat propelling apparatus secura'ble to the transom of a boat and comprising an inboard prime mover and an outboard propeller unit having its propeller shaft driven from the drive shaft of the prime mover by a belt which extends over the top of the transom. A rigid supporting structure of substantially inverted U- shape provides a common mounting means for the prime mover and the propeller unit. The legs of the supporting structure straddle the transom of a boat having the apparatus mounted thereon, and the prime mover is carried by the inboard leg while the propeller unit is carried by the bight bridging the upper ends of the legs.

10 Claims, 11 Drawing Figures PATENTEDJun 4 1914 3814047 sum u [If a PATENTEUJUN 4 1914- 3. 8 1 4. 047

SHEEI 5 0F 8 INBOARD-OUTBOARD BOAT IROIPELLING APPARATUS This invention relates to propulsion devices for small boats, and has more particular reference to propelling apparatus which mounts on the transom of a boat and has an outboard propelling unit driven from a prime mover located at the inboard side of the transom.

It is one of the purposes of the invention to provide a so called inboard-outboard boat propelling apparatus of the type referred to above, which features a prime mover in the form of a small, compact, air cooled internal combustion engine.

Efforts have been made in the past to provide inboard-outboard boat propulsion devices of the type described, but difficulties were always encountered in the mounting of the internal combustion engine and the propeller unit at opposite sides of the transom of the boat. Some of these difficulties may have resulted from the inability satisfactorily to provide for adjustment of the propelling unit to dispose it in the position best suited for propulsion, as well as to provide for tilting of the propelling unit to an inoperative position with the propeller at its lower end elevated.

Accordingly, it is another purpose of this invention to provide an exceptionally efficacious way of mounting an inboard-outboard type of boat propelling apparatus on the transom of a boat, featuring a rigid supporting structure which is common to the prime mover and to the propelling unit and not only provides for tilting of the latter relative to the prime mover to an inoperative position with the propeller end of the unit elevated, but also provides for bodily adjustment of the supporting structure itself to positions holding the propelling unit in the attitude best suited for propulsion.

Another object of the invention resides in the provision of an inboard-outboard type of boat propulsion device featuring a supporting structure upon which either a vertical or a horizontal shaft internal combustion engine can be readily detachably mounted.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate several complete examples of embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a fragmentary perspective of the rear portion of a boat having a propulsion device of this invention mounted on the transom thereof;

FIG. 2 is a top view thereof with portions broken away to show internal construction;

FIG. 3 is a side elevation of the apparatus, taken on the line.3-3 in FIG. 2;

FIG. 4 is an enlargement of a portion of the mechanism seen in FIG. 2, showing the parts in greater detail;

FIG. 5 is a sectional view of the propelling unit taken on the line 5-5, in FIG. 4;

FIGS. 6 and 7 are cross sectional views through the propelling unit, taken on the lines 6-6 and 7-7, respectively, in FIG. 3;

FIG. 8 is a view similar to FIG. 3, but showing a horizontal shaft internal combustion engine as the source of power;

FIG. 9 is a view similar to FIGS. 3 and 8 but showing a further modification of the invention;

FIG. 10 is a'fragmentary perspective view on the order of FIG. 1, but showing one way in which the propulsion device can be neatly concealed on the rear portion of a boat; and

FIG. 11 is a view similar to FIG. 2 but showing a slightly modified form of belt tensioning clutch device.

Referring now more particularly to the accompanying drawings, it will be seen that the boat propelling apparatus of this invention comprises two main compo nents, namely a prime mover l0, and an elongated propeller unit 11 driven by the prime mover.

These two components are carried by a rigid supporting structure 12, which provides for mounting the apparatus on the transom 13 of a small boat 14 with the prime mover at the inboard side of the transom and the propeller unit at its outboard side.

The supporting structure 12 is of inverted U-shape having upright inboard and outboard legs 16 and 17, respectively, which straddle the transom l3, and a bight 18 which rigidly joins the legs at their upper ends and extends fore and aft across the top of the transom 13. The supporting structure can be a casting having its inboard leg formed in one piece with the remainder of the supporting structure, but the inboard leg is here shown as comprised of a separate piece part which is either welded to the forward end of the bight I8 or securely but detachably bolted to the underside thereof as seen at 20 in FIG. 9.

According to this invention, the prime mover 10 is a small, single cylinder air cooled internal combustion engine preferably of the vertical shaft type. It is mounted on a seat 22 formed on the lower end of the inboard leg 16 of the supporting structure, and it has a drive pulley 23 on the upper end of its crankshaft 24. Screws 25 preferably detachably secure the engine to the seat, and facilitate its removal for servicing when necessary.

The upper housing portion 26 of the propeller unit 11 is pivotally supported on a hinge pin 27 carried by the bight 18 of the supporting structure, to mount the propeller unit for tilting motion from a substantially vertical operating position to an inoperative tilted position with its propeller 28 elevated. The hinge pin 27 is disposed on a horizontal axis crosswise of the bight 18, substantially medially of the inboard and outboard legs of the supporting structure, and is located a distance above the upper edge of the transom 13 upon which the propelling apparatus is mounted.

The outboard leg 17 of the supporting structure is substantially semicircular in cross section, having its concave side facing rearwardly, away from the transom. It is formed to nestingly receive a tubular part 29 of the upper housing portion 26 on the propeller unit 17, to thus not only define the operating position of the unit but to also bear the forward thrust imposed thereon by the propeller 28 during operation of the propelling apparatus.

In those embodiments of the invention seen in FIGS. 3 and 8, the propelling apparatus is readily dismountably secured to the transom 13 by means of a clamp 32. The clamp is also of inverted U-shape in that it has a bight 33 which rests uponand extends fore and aft over the top of the transom, and front and rear jaws 34 and 35 which extend downwardly from the bight and lie at the inboard and outboard sides, respectively, of the transom. Screws 36 with swivel-type handles 36 thereon provide for securement of the clamp to the transom.

The bight portion 18 of the supporting structure 12 extends over the bight 33 of the clamp, between upwardly projecting flanges 37 on the latter. These flanges extend over the bight of the clamp and down each of its legs 34-35. The flange portions 38 on the front leg 34 of the clamp embrace the inboard leg 16 of the supporting structure, which leg is pivotally connected to the clamp flanges 38 on either side thereof by means of a hinge pin 40. The pin 40 is disposed on a horizontal axis crosswise of the bight portions on the supporting structure and the clamp upon which it is pivotally mounted. Hence, the supporting structure can be tilted back and forth relative to the clampand to the transom, to dispose the propeller unit 11 in the upright attitude best suited for propulsion.

The flange portions 41 on the rear jaw of the clamp 32 embrace the outboard leg 17 of the supporting structure and have curved slots 42 therein which are concentric to the axis of the hinge pin 40. A threaded stud 43 on each side of the outboard leg 17 projects laterally therefrom and through the adjacent arcuate slot 42 to receive a wing nut 44. When the wing nuts are tightened, they hold the supporting structure 12 at the selected position of angular adjustment about the axis of its hinge 40.

This is an important feature ofthe invention, inasmuch as it enables proper orientation of the propeller unit 11, regardless of the angle of the transom 13 on a boat having the propelling apparatus mounted thereon.

It is also important to note that the seat 22 on the inboard leg of the supporting structure is designed and located to hold the engine spaced above the bottom of the boat and with its drive pulley 23 in a horizontal plane a slight distance above the top edge of the transom 13. The drive pulley is located immediately below a rope starter hub 46, although an electric engine starter 47 may be provided to facilitate starting the engme.

The construction of the propeller unit 11 constitutes another feature of the invention. It has an upright propeller drive shaft 49 mounted within an elongated tubular steering member 50. The steering member 50, in turn, is mounted for rotary movement on its axis, within the tubular housing part 29 of the propeller unit 11 by means of bearings 51 and 52 best seen in FIG. 5. The propeller drive shaft projects upwardly out of the tubular steering member 50 and has a pulley 53 fixed thereto in the plane of the drive pulley on the engine, with which it is drivingly connected by means of an endless belt 54.

The tubular steering member 50 extends downwardly out of the lower end of the housing part 26 and a propeller housing 55 is secured to the bottom of the steering member, to turn therewith. The propeller 28 is mounted in the propeller housing to rotate on a substantially horizontal axis. Accordingly, to effect steering of the boat, the operator is merely required to rotate the tubular steering member 50 in one direction or the other, to carry the propeller to one side or the other of a vertical plane containing the axis of the steering member and normal to the transom 13.

According to this invention, rotary steering motion can be imparted to the propeller housing 55 by means of an enlongated tiller 56, which extends forwardly from the top of the propeller unit, adjacent to one side of the internal combustion engine 10. The forward end of the tiller is provided with a hand grip 57 and its rear end portion is pinned as at 58 to the hub 59 of a sprocket 60 (see FIG. 5). The sprocket is journalled for rotation about the vertical axis of a stud 61 which is anchored in the bottom wall 62 of the pan-like top of the upper housing structure 26.

The sprocket is thus drivingly connected with the tiller to be rotated in one direction or the other by swinging the tiller in the corresponding direction. The sprocket is also drivingly connected with the tubular steering member 50 by means of a timer type chain 63 trained around it and a companion sprocket 64 on the tubular steering member, beneath the pulley 53.

The upper end portion of the sprocket hub 59 projects through a cover 65 on the pan-like top of the housing structure 26, and it has a shoulder 66 thereon to limit downward swinging motion of the tiller about the axis of the pin 58 beyond the substantially horizontal position of the tiller shown. Hence, the operator can also exert downward force on the grip 57 of the tiller in order to effect tilting of the propeller unit 11 to an inoperative position on its hinge 27. Such tilting of the unit is facilitated by reason of the fact that the stud 61 mounting the tiller and the sprocket 60 is located on an axis which lies in a transverse vertical plane containing the axis of the hinge pin 27 about which the propeller unit tilts.

A belt tightener pulley 67 is also movably mounted on the bight portion 18 of the supporting structure 12 to provide for tightening of the belt 54 into driving engagement with the pulleys on the engine and propeller drive shafts, and for loosening of the belt into nondriving relation with respect to those pulleys. The belt tightenerlpulley can be arranged to bear upon either the inner side of the belt 54 as seen in FIG. 2, or upon the outer side of the belt in the manner shown in FIG. 11. In either case, the belt tightener pulley 67 is normally held by a spring loaded overcenter type toggle linkage such as indicated at 68, in an operative position such as seen in FIG. 2 and in broken lines in FIG. 11, from which it can be moved to a toggle collapsed inoperative position such as shown in solid lines in FIG. 11. A hand control lever 69 is accessible at a forward portion of a shield 70 around the top of the engine, to provide for clutching and declutching operation of the belt tightener pulley. The adjacent control lever 69 is connected with the throttle valve of the engine in the customary way.

Attention is directed to the fact that the axis of the hinge 27 about which the propeller unit tilts lies in the plane of the belt 54 and the pulleys 23 and 53 drivingly connected thereby. With this disposition of the hinge axis, the belt 54 interferes least with tilting of the propeller unit to its inoperative position.

The embodiment of the invention seen in FIG. 9 is like that just described except that a number of resilient mounting members 75 of a conventional type are em ployed to secure the boat propelling apparatus to the transom 13 of the boat. These resilient mounting members are fastened to the inboard leg 16 of the supporting structure, and are bolted or otherwise secured to the transom 13.

This invention also provides for the use of a horizontal shaft internal combustion engine 77 as a prime mover, instead of the vertical shaft engine described above. FIG. 8 reveals how such a horizontal shaft engine can be readily mounted at the inboard side of the transom 13 of the boat, with the propeller unit at the outboard side of the transom as before.

As seen in FIG. 8, the supporting structure 112 is nearly identical to that seen in FIG. 3 for example; the only difference being in the construction of the inboard leg 116. In this case, the inboard leg 116 has an upright transverse wall 78 which is spaced somewhat farther forwardly of the inner jaw of the clamp 32 than formerly, and to which the engine is secured as by machine screws 79.

The crankshaft 80 of the engine projects rearwardly through an opening in the wall 78, and the drive pulley 81 is secured thereto so as to be located in the space between the wall 78 and the transom 13. The engine is again in this case mounted on the inboard leg of the supporting structure in spaced relation to the bottom of the boat, but at a slightly lower elevation than the vertical shaft engine.

Inasmuch as the drive pulley 81 rotates about a horizontal axis while the driven pulley 53 on the upper end of the propeller drive shaft rotates on a substantially vertical axis in the operative position of the propeller unit 11, the belt 82 drivingly connecting these pulleys is trained over an idler unit generally designated 83. The idler unit comprises a pair of pulleys 84, one for each stretch of the belt 82, mounted on a common horizontal idler shaft 85 having its axis parallel to the axis of the hinge pin 27 about which the propeller unit tilts.

The idler unit also provides a clutch device, by which the propeller drive shaft may be drivingly connected with the engine pulley or disconnected therefrom at will. For this purpose, the idler unit is supported from the inboard leg 116 of the supporting structure for bodily swinging motion in opposite directions about a pivot 86 having itsaxis parallel to that of the hinge pin 27, toward and from an operative position at which the belt 82 is tightened into driving engagement with the pulleys 81 and 53. One or more arms 87 having one end fixed to the pivot 86 and freely rotatably carrying the idler shaft 85 in their outer ends are provided for this purpose.

The arms 87 extend generally upwardly and rearwardly from the pivot 86, and support the idler unit for generally fore and aft swinging motion, toward and from the inner jaw 34 of the clamp 32. In the operative or belt tight position of the idler unit, its pulleys 84 are located with their upper peripheral portions in the horizontal plane of the driven pulley 53 and their forwardly facing peripheral portions in the vertical plane of the drive pulley 81. When swung toward the clamp 32, the drive belt 82 is slackened and the drive between the pulleys 81 and 53 is interrupted.

Again in this case, the idler pulley unit can be held in either its operative or inoperative positions by spring loaded overcenter type toggle linkage generally designated 88, one link 89 of which is pivotally connected to one of the arms 87. The other link 911 is pivotally supported as at 91 from a post 92 fixed to and extending rearwardly from the upright wall 78 of the inboard leg 116 of the supporting structure. These links, of course, are pivotally connected at the knee 93 of the toggle.

A toggle actuating rod 94 connects with a hand lever or the like (not shown) to provide: for manually cocking and/or collapsing of the toggle joint.

The cocked position of the toggle joint provided by the overcenter linkage 88 is defined by the engagement of a lug 95 on the link 91) with an abutment 96 on the post 92. The collapsed position of the toggle is defined by the engagement of a heel 98 on one of the arms 87 with the rear side of the engine supporting wall 78.

In all embodiments of the invention described, the propeller unit can be locked to the outboard leg 17 of the supporting structure after the propeller has been moved more than 90 in either direction out of a straight head position lying in the aforesaid vertical plane containing the axis of the tubular steering member 50, to then prevent the propeller unit from tilting about the axis of its hinge 27 due to rearward thrust of the propeller on the propeller unit. This locking feature is afforded by the expedient seen best in FIG. 7, wherein a 90 segment has been shown as secured to the bottom of the outboard leg 17 of the supporting structure to engage in a groove formed in a segment-like flange 121 on a collar 122 fixed to the tubular steering member 50. Thesegment 110, of course, is stationary, and the flange 121 turns with the tubular steering member topositions embracing the segment 110 just before the steering member is turned far enough to cause the propeller to exert rearward force on the propeller unit tending to separate it from the backup provided by the outboard leg of the supporting structure.

FIG. 10 indicates how an inboard-outboard type boat propelling apparatus like that seen in FIG. 9 can be mounted on a boat with its propeller unit concealed from view. In this case, the transom (not shown) upon which the propelling apparatus is mounted is in the nature of a bulkhead which is spaced. a distance forwardly of what might be termed a divided transom at the extreme rear of the boat, having spaced apart side by side transom portions 131 defining a well 132 becween them of a size to accommodate the propeller unit. The sides of the well, of course, are closed off by walls (not shown), and a panel 133 is attached to the rear of the propeller unit to be in the common plane of the side by side transom portions 131 when in its operative propelling position.

Steering, in this case, is accomplished by controls located remotely in the bow portion of the boat and connecting with one or the other of the sprockets 60 or 65.

The boat is also preferably provided with deck portions 134 flanking and in the plane of the cover 65 on the top of the propeller unit.

Although shown only in FIG. 11,. it is preferable in all embodiments of the invention to provide belt retainers such as those indicated by the numeral 135 in FIG. 11, to guard against accidental displacement of the driving belt from the pulleys it connects. From the foregoing description, together with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides an inboard-outboard propelling apparatus which is ideally suited for the propulsion of small boats.

I claim:

1. Boat propelling apparatus of the type having a clamp secureable to the transom of a boat, and having a prime mover with output means disposed at the inboard side of the transom and a propeller unit outboard thereof having a propeller drive shaft driven from said output means, characterized by:

A. a rigid supporting structure having an upper portion extending rearwardly across the top of the transom, and having legs extending downwardly therefrom, one along the inboard side of the transom and the other along the outboard side thereof;

B. means mounting the propeller unit on the supporting structure for tilting motion relative to the outboard leg thereof, toward and from an operative position defined by said outboard leg;

C. prime mover mounting means on said inboard leg mounting the prime mover in a position forwardly of said inboard leg and hence at the inboard side of the transom,.with substantially the entire prime mover below the upper edge of the transom;

D. pivot means on the clamp mounting the supporting structure thereon for bodily tilting movement relative thereto about a horizontal axis crosswise of said upper portion of the supporting structure;

E. said outboard leg being engageable by the propeller unit to bear the forward thrust of the propeller thereon in operation and being tiltable with the supporting structure to provide for adjustment of the operating position of the propeller unit;

F. and means interengageable with the clamp and the supporting structure to releasably hold the latter in adjusted position and against movement relative to the clamp and hence the transom to which the clamp is secured.

2. The boat propelling apparatus of claim 1, further characterized by:

A. the mounting means on said inboard leg comprising a substantially horizontal seat to which the prime mover is secured;

B. and the prime mover comprising a vertical shaft internal combustion engine having its output means uppermost and above the level of said clamp.

3. The boat propelling apparatus of claim 2, further characterized by:

A. said output means comprising a pulley mounted on the crankshaft of the engine;

B. the propeller drive shaft having a pulley in substantially the same horizontal plane as the engine pulley;

C. an endless belt drivingly connecting said pulleys;

D. and the means mounting the propeller unit on the supporting structure constraining the propeller unit to bodily tilting motion about a horizontal axis lying substantially in said plane.

4. The boat propelling apparatus of claim 1, wherein said portion of the supporting structure provides an elongated upright backup for the propeller unit.

5. The boat propelling apparatus of claim 4, further characterized by: i

A. a tiller mounted on the propeller unit for swinging movement relative thereto about an upright axis, back and forth at a level above the top of the prime mover;

B. a propeller housing on the lower end portion of the propeller unit;

C. and means providing an operating connection between the tiller and the propeller housing by which the latter can be turned for steering purposes in consequence of swinging of the tiller about said upright axis. v

6. The boat propelling apparatus of claim I wherein said prime mover is a vertical shaft internal combustion engine having an output pulley on the upper end of its crankshaft, at a level above the supporting structure;

wherein the propeller unit is supported by said hinge means and has a normally upright propeller drive shaft with a driven pulley on its upper end coplanar with said output pulley;

wherein said pulleys are drivingly connected by means of an endless belt;

and wherein the axis of said hinge means on the bight is between said pulleys and in the plane thereof.

7. The boat propelling apparatus of claim 1, further characterized by:

A. a substantially upright wall on said inboard leg, ex-

tending transversely of said upper portion of the supporting structure and to which the prime mover is secured;

B. the prime mover comprising a horizontal shaft internal combustion engine having an output pulley disposed adjacent to the rear side of the engine supporting wall and substantially parallel thereto;

C. a pulley on the upper end of the propeller drive shaft normally disposed in a horizontal plane;

D. an idlerpulley unit carried by said inboard leg above the output pulley and forwardly of the pulley on the propeller drive shaft;

E. and an endless belt trained around said output and propeller drive shaft pulleys and over the pulleys of the idler unit, to drivingly connect the propeller drive shaft with the output pulley.

8. Boat propelling apparatus, comprising A. a clamp to mount the apparatus on the transom of a boat, said clamp having inboard .and outboard jaws and means to secure the clamp to a boat transom;

B. a rigid supporting structure pivotally mounted on the inboard jaw of the clamp for tilting motion about a horizontal axis generally parallel to the upper edge of a transom upon which the apparatus is mounted;

C. a prime mover carried by the supporring structure at a location directly ahead of said inboard jaw; D. an elongated outboard propeller unit pivotally mounted on an upper portion of the supporting structure for tilting motion from an upright operating position behind the transom of a boat defined by its engagement with a portion of said supporting structure to an inoperative position at which its propeller end portion is elevated and spaced rearwardly from said portion of the supporting structure;

E. and cooperating means on the outboard jaw of the clamp and the supporting structure for holding the latter against movement out of a selected position relative to the clamp and hence the transom to which the clamp is secured.

9. Boat propelling apparatus having an outboard propeller unit and an inboard prime mover, characterized by:

A. a clamp having inboard and outboard jaws to embrace the transom of a boat;

B. a rigid supporting structure of substantially inverted U-shape providing spaced apart inboard and outboard legs to straddle the transom of a boat, and a bight joining said legs at their tops;

C. means mounting the supporting structure on the clamp comprising pivot means connecting the inboard jaw of the clamp and the inboard leg of the supporting structure and providing for bodily tilting adjustment of the latter about a horizontal axis transversly of its bight;

D. securement means interconnecting the rigid supporting structure and the clamp to secure the same against relative motion in a selected position of adjustment;

E. prime mover mounting means on said inboard leg mounting the prime mover in a position directly forwardly adjacent to said inboard leg with the major portion of the prime mover below the level of the bight of said rigid supporting structure:

F. and hinge means on said bight mounting the outboard propeller unit on the supporting structure for tilting motion about an axis parallel to that of said pivot means, toward and from an operative position defined by its engagement with the outboard leg of the supporting structure.

10. Boat propelling apparatus of the type having a clamp secureable to the transom of a boat, and having a'prime mover with output means disposed at the inboard side of the transom and a propeller unit outboard thereof having a propeller drive shaft driven from said output means, characterized by:

A. a rigid supporting structure having an upper portion to extend rearwardly across the top of the transome and having legs extending downwardly there- W from, one along the inboard side of the transon and the other along the outboard side thereof;

B. said inboard leg having an upright wall which extends transversely of said upper portion of the supporting structure and to which the prime mover is secured;

C. pivot means on the clamp mounting the supporting structure thereon for bodily tilting movement relative thereto about a horizontal axis crosswise of said upper portion of the supporting structure;

D. said outboard leg being engageable by the propeller unit to bear the forward thrust of the propeller thereon in operation and to define the operating position of said unit, said outboard leg being tiltable with the supporting structure to provide for adjustment of the operating position of the propeller unit;

E. means interengageable with the clamp and said outboard leg of the supporting structure to releasably hold the latter in adjusted position;

E the prime mover comprising a horizontal shaft intemal combustion engine having an output pulley disposed adjacent to the rear side of the upright wall on said inboard leg and substantially parallel to said wall;

G. a pulley on the upper end of the propeller drive shaft normally disposed in a horizontal plane;

H. an idler pulley unit carried by said inboard leg above the output pulley and forwardly of the pulley on the propeller drive shaft;

1. an endless belt trained around said output and propeller drive shaft pulleys and over the pulleys of the idler unit, to drivingly connect the propeller drive shaft with the output pulley;

l structure mouting the idler pulley unit on said inboard leg for bodily movement between slack belt and tight belt positions;

K. and spring loaded overcenter type toggle linkage providing a toggle joint mechanism connected with the idler unit to releasably hold it in each of said positions thereof. 

1. Boat propelling apparatus of the type having a clamp secureable to the transom of a boat, and having a prime mover with output means disposed at the inboard side of the transom and a propeller unit outboard thereof having a propeller drive shaft driven from said output means, characterized by: A. a rigid supporting structure having an upper portion extending rearwardly across the top of the transom, and having legs extending downwardly therefrom, one along the inboard side of the transom and the other along the outboard side thereof; B. means mounting the propeller unit on the supporting structure for tilting motion relative to the outboard leg thereof, toward and from an operative position defined by said outboard leg; C. prime mover mounting means on said inboard leg mounting the prime mover in a position forwardly of said inboard leg and hence at the inboard side of the transom, with substantially the entire prime mover below the upper edge of the transom; D. pivot means on the clamp mounting the supporting structure thereon for bodily tilting movement relative thereto about a horizontal axis crosswise of said upper portion of the supporting structure; E. said outboard leg being engageable by the propeller unit to bear the forward thrust of the propeller thereon in operation and being tiltable with the supporting structure to provide for adjustment of the operating position of the propeller unit; F. and means interengageable with the clamp and the supporting structure to releasably hold the latter in adjusted position and against movement relative to the clamp and hence the transom to which the clamp is secured.
 2. The boat propelling apparatus of claim 1, further characterized by: A. the mounting means on said inboard leg comprising a substantially horizontal seat to which the prime mover is secured; B. and the prime mover comprising a vertical shaft internal combustion engine having its output means uppermost and above the level of said clamp.
 3. The boat propelling apparatus of claim 2, further characterized by: A. said output means comprising a pulley mounted on the crankshaft of the engine; B. the propeller drive shaft having a pulley in substantially the same horizontal plane as the engine pulley; C. an endless belt drivingly connectIng said pulleys; D. and the means mounting the propeller unit on the supporting structure constraining the propeller unit to bodily tilting motion about a horizontal axis lying substantially in said plane.
 4. The boat propelling apparatus of claim 1, wherein said portion of the supporting structure provides an elongated upright backup for the propeller unit.
 5. The boat propelling apparatus of claim 4, further characterized by: A. a tiller mounted on the propeller unit for swinging movement relative thereto about an upright axis, back and forth at a level above the top of the prime mover; B. a propeller housing on the lower end portion of the propeller unit; C. and means providing an operating connection between the tiller and the propeller housing by which the latter can be turned for steering purposes in consequence of swinging of the tiller about said upright axis.
 6. The boat propelling apparatus of claim 1 wherein said prime mover is a vertical shaft internal combustion engine having an output pulley on the upper end of its crankshaft, at a level above the supporting structure; wherein the propeller unit is supported by said hinge means and has a normally upright propeller drive shaft with a driven pulley on its upper end coplanar with said output pulley; wherein said pulleys are drivingly connected by means of an endless belt; and wherein the axis of said hinge means on the bight is between said pulleys and in the plane thereof.
 7. The boat propelling apparatus of claim 1, further characterized by: A. a substantially upright wall on said inboard leg, extending transversely of said upper portion of the supporting structure and to which the prime mover is secured; B. the prime mover comprising a horizontal shaft internal combustion engine having an output pulley disposed adjacent to the rear side of the engine supporting wall and substantially parallel thereto; C. a pulley on the upper end of the propeller drive shaft normally disposed in a horizontal plane; D. an idler pulley unit carried by said inboard leg above the output pulley and forwardly of the pulley on the propeller drive shaft; E. and an endless belt trained around said output and propeller drive shaft pulleys and over the pulleys of the idler unit, to drivingly connect the propeller drive shaft with the output pulley.
 8. Boat propelling apparatus, comprising A. a clamp to mount the apparatus on the transom of a boat, said clamp having inboard and outboard jaws and means to secure the clamp to a boat transom; B. a rigid supporting structure pivotally mounted on the inboard jaw of the clamp for tilting motion about a horizontal axis generally parallel to the upper edge of a transom upon which the apparatus is mounted; C. a prime mover carried by the supporring structure at a location directly ahead of said inboard jaw; D. an elongated outboard propeller unit pivotally mounted on an upper portion of the supporting structure for tilting motion from an upright operating position behind the transom of a boat defined by its engagement with a portion of said supporting structure to an inoperative position at which its propeller end portion is elevated and spaced rearwardly from said portion of the supporting structure; E. and cooperating means on the outboard jaw of the clamp and the supporting structure for holding the latter against movement out of a selected position relative to the clamp and hence the transom to which the clamp is secured.
 9. Boat propelling apparatus having an outboard propeller unit and an inboard prime mover, characterized by: A. a clamp having inboard and outboard jaws to embrace the transom of a boat; B. a rigid supporting structure of substantially inverted U-shape providing spaced apart inboard and outboard legs to straddle the transom of a boat, and a bight joining said legs at their tops; C. means mounting thE supporting structure on the clamp comprising pivot means connecting the inboard jaw of the clamp and the inboard leg of the supporting structure and providing for bodily tilting adjustment of the latter about a horizontal axis transversly of its bight; D. securement means interconnecting the rigid supporting structure and the clamp to secure the same against relative motion in a selected position of adjustment; E. prime mover mounting means on said inboard leg mounting the prime mover in a position directly forwardly adjacent to said inboard leg with the major portion of the prime mover below the level of the bight of said rigid supporting structure: F. and hinge means on said bight mounting the outboard propeller unit on the supporting structure for tilting motion about an axis parallel to that of said pivot means, toward and from an operative position defined by its engagement with the outboard leg of the supporting structure.
 10. Boat propelling apparatus of the type having a clamp secureable to the transom of a boat, and having a prime mover with output means disposed at the inboard side of the transom and a propeller unit outboard thereof having a propeller drive shaft driven from said output means, characterized by: A. a rigid supporting structure having an upper portion to extend rearwardly across the top of the transome and having legs extending downwardly therefrom, one along the inboard side of the transon and the other along the outboard side thereof; B. said inboard leg having an upright wall which extends transversely of said upper portion of the supporting structure and to which the prime mover is secured; C. pivot means on the clamp mounting the supporting structure thereon for bodily tilting movement relative thereto about a horizontal axis crosswise of said upper portion of the supporting structure; D. said outboard leg being engageable by the propeller unit to bear the forward thrust of the propeller thereon in operation and to define the operating position of said unit, said outboard leg being tiltable with the supporting structure to provide for adjustment of the operating position of the propeller unit; E. means interengageable with the clamp and said outboard leg of the supporting structure to releasably hold the latter in adjusted position; F. the prime mover comprising a horizontal shaft internal combustion engine having an output pulley disposed adjacent to the rear side of the upright wall on said inboard leg and substantially parallel to said wall; G. a pulley on the upper end of the propeller drive shaft normally disposed in a horizontal plane; H. an idler pulley unit carried by said inboard leg above the output pulley and forwardly of the pulley on the propeller drive shaft; I. an endless belt trained around said output and propeller drive shaft pulleys and over the pulleys of the idler unit, to drivingly connect the propeller drive shaft with the output pulley; J. structure mouting the idler pulley unit on said inboard leg for bodily movement between slack belt and tight belt positions; K. and spring loaded overcenter type toggle linkage providing a toggle joint mechanism connected with the idler unit to releasably hold it in each of said positions thereof. 